The present invention relates generally to a connecting adapter for connecting a weld electrode to a welding device, particularly a resistance welding device. More specifically, the present invention relates to a one-piece adapter, one end of which may be removably and sealably installed to a tip holder portion of a resistance welding device, while the opposite end is adapted to receive a weld electrode. The adapter is easy to install and remove, and is inexpensive to manufacture. Consequently, the adapter can be easily replaced as it wears.
Resistance welding is a commonly employed technique for joining metallic work pieces via electric current. There are several forms of resistance welding, including spot welding, seam welding, projection welding, and butt welding. However, all forms of resistance welding operate to join work pieces by causing the localized heating thereof. The localized heating is sufficient to produce a molten weld pool between the work pieces. Upon cooling, the weld pool forms a weld nugget that joins the work pieces.
As stated, it is necessary to generate heat to perform resistance welding. The amount of heat generated depends on several factors, including the electrical resistance and thermal conductivity of the components to be joined, and the time that the current is applied. As such, it is desirable to conduct the electric current used to produce this heat as efficiently as possible. Consequently, although other conductive metals may be used, copper is commonly utilized to form the current carrying components of a resistance welding device. These components may include, for example, a gun arm, a weld tip holder, a connecting adapter, and a weld electrode. The use of copper helps to facilitate the generation of enough heat to cause a localized melting of the work pieces to be joined. Copper also exhibits a high thermal conductivity in comparison to most other metals. The high conductivity of copper helps to prevent overheating of the welding device components by ensuring that the heat produced by the electric current is generated in the work pieces to be joined, instead of in the components of the welding device. Overheating of the weld electrodes, for example, can be detrimental to the appearance of the work piece surfaces, and can also cause degradation of the electrodes. Water or another fluid is also typically circulated through or around the interior of the weld electrodes to provide additional cooling.
Resistance welding also requires that the weld electrodes be held against the work pieces under force during the welding process. The electrical resistance across the interface of the electrodes and the work pieces is affected by the amount of force that is exerted against the work pieces by the electrodes. By knowing the material properties of the work pieces, the amount of force exerted by the electrodes can be adjusted to create substantially immediate heat at the interface between the work pieces. The amount of force is adjusted to provide sufficient contact for welding, while also ensuring that expulsion, or weld spatter is minimized.
While copper is an excellent material for efficiently transferring electrically-produced heat to the work pieces to be joined, it is also a soft material. Consequently, the various copper components of typical resistance welding devices are prone to wear and/or damage. For example, weld electrodes wear down during use as a result of heat generated by the welding process, and also due to the force they are required to exert against the work pieces upon which they operate. Consequently, in order to keep a weld electrode in satisfactory welding condition, the weld electrode is typically subjected to a periodic cutting or shaping process commonly referred to as “tip dressing”.
Eventually, however, the weld electrode will wear beyond an acceptable limit, and must then be replaced. On many resistance welding devices, the process of electrode replacement involves removing the old electrode and installing a new electrode to a tip holder portion of the welding device. A weld electrode is commonly removed by force, such as with pliers, wrenches, hammers, or other similar tools suitable for dislodging the electrode from the tip holder. The tip holder/electrode design of a resistance welding device can vary considerably. For example, certain tip holders are designed with a female cavity that is designed to receive a shank portion of a connecting adapter or a specialized electrode having a protruding male shank. The connecting adapter or electrode may be tapped into the tip holder using a hammer, for example. Alternatively, the tip holder may be equipped with a protruding male portion, over the end of which may be placed an electrode. Again, the electrode may be installed using a hammer or similar tool. Under either of the above scenarios, however, the components are generally moderately force fit by employing tapered mating portions and taking advantage of the generally malleable nature of the copper material from which they are formed.
As can be surmised from the above description, due to the softness of the copper material, electrode replacement will eventually have a detrimental effect on the condition of the mating components of the resistance welding device. For example, in the above, former example, repeated removal/installation of connecting adapters or electrodes to/from the cavity in the weld tip holder will eventually lead to the deformation thereof. Similarly, repeated removal/installation of electrodes to/from the protruding male portion of weld tip holder in the above, latter example, will eventually lead to the deformation thereof, and to possible deformation of a larger portion of the tip holder as a result of repeated impact. Consequently, such components require periodic replacement.
One problem with known resistance welding devices is that there has been, heretofore, no easy, quick, and inexpensive way to replace such components. For example, when a tip holder equipped with an adapter/electrode receiving cavity needs to be repaired or replaced, the entire tip holder must generally be removed from the gun arm. Such a process can require a significant amount of time to accomplish, as the tip holder is typically attached to the gun arm by a number of fasteners. Additionally, there are generally cooling lines running through the gun arm and into the tip holder, so re-sealing must be ensured. Further, such a process can be expensive, as in addition to the cost associated with repair or replacement of the tip holder, a plurality of spare tip holders must be kept stocked and available.
Therefore, as can be discerned from the foregoing discussion, it is desirable to be able to attach a weld electrode to a resistance welding device in such a manner that removal/installation of the electrode can be accomplished in an efficient manner. It is also desirable that the means of attaching the electrode to the welding device be as inexpensive as possible, thereby providing for low cost replacement. The weld electrode connecting adapter of the present invention satisfies this need. The adapter of the present invention functions as a low cost means of facilitating quick and easy connection of a weld electrode to a resistance welding device. More specifically, one end of the adapter of the present invention may be sealably threaded into a tip holder portion of a resistance welding device. The opposite end of the adapter is designed to receive a weld electrode. The adapter is preferably made from copper, but other conductive materials may also be employed for its construction.
One embodiment of the adapter of the present invention is provided with parallel threads for threading into a corresponding threaded cavity in the tip holder portion of a resistance welding device. The adapter preferably has a passageway extending longitudinally therethrough to allow for the circulation of cooling water to the electrode. An o-ring may be provided in the vicinity of the threaded portion of the adapter to prevent leakage of cooling fluid from around the threads. Preferably, a receiving groove, or channel, is also provided in the receiving cavity of the tip holder to receive the o-ring and to provide a proper seal. The electrode receiving end of the adapter is preferably tapered to receive a like-tapered electrode. The adapter can generally be installed to a tip holder with a common wrench, although it may also be designed to require a specialized installation/removal tool. In certain embodiments, an electrode can be installed to the adapter in the normal fashion—by tapping it into position with a hammer or other acceptable tool.